border-1px-bottom($color)
  position:relative
  &:before
    display :block
    position absolute
    left : 0
    bottom : 0
    width 100%
    border-top : 1px solid $color
    content :' '
border-1px-top($color)
  position:relative
  &:after
    display :block
    position absolute
    left : 0
    top : 0
    width 100%
    border-top : 1px solid $color
    content :' '


bg-image($url)
  background-image :url($url+"@2x.png")
  @media (-webkit-min-device-pixel-ratio:3),(-min-device-pixel-ratio:3)
    background-image :url($url+"@3x.png")
